/Engine/Source/Runtime/Slate/Public/Framework/Application/SlateApplication.h
Called when a touchpad touch is started (finger down) when polling game device state
void ProcessTouchStartedEvent ( const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FGenericWindow](API\Runtime\ApplicationCore\GenericPlatform\FGenericWindow) > & PlatformWindow, const [FPointerEvent](API\Runtime\SlateCore\Input\FPointerEvent) & InTouchEvent )